The present invention relates to an axial flow type gas laser oscillating apparatus for passing laser gas in a discharge tube.
FIG. 37 shows an example of a schematic structure of a gas laser oscillating apparatus known as axial flow type. Referring to FIG. 37, the axial flow type gas laser oscillating apparatus (hereinafter referred to simply as xe2x80x9cAFGLOxe2x80x9d) is explained below. As shown in FIG. 37, the AFGLO is mainly composed of a laser resonator, a power supply unit, and a laser gas circulation part.
The laser resonator further comprises a discharge tube 1 having a discharge area 5, a rear mirror (hereinafter referred to simply as xe2x80x9cRMxe2x80x9d) 6, and an output mirror (hereinafter referred to simply as xe2x80x9cOPMxe2x80x9d) 7. The discharge tube (hereinafter referred to simply as xe2x80x9cDTxe2x80x9d) 1 is composed of glass or other dielectric material, and electrodes 2, 3 are provided near both ends of the DT 1. In the space of the DT 1 enclosed by the electrodes 2, 3, the discharge area (hereinafter referred to simply as xe2x80x9cDAxe2x80x9d) 5 is formed. Plural DAs 5 are disposed between the RM 6 and OPM 7. The RM 6 is a reflector having a reflectivity of about 100%. The OPM 7 is a partial reflector, and a laser beam 8 is emitted from the OPM 7.
The power supply unit 4 is connected to the electrodes 2, 3 in order to discharge in the DA 5.
The laser gas circulating part (hereinafter referred to simply as xe2x80x9cLGCPxe2x80x9d) comprises a blower 13, heat exchangers 11, 12, a laser gas passage 10, DT 1, and a laser gas lead-in part 14. The laser gas lead-in part 14 is a part for leading the laser gas into the DT 1 from the laser gas passage 10. The laser gas circulates the LGCP for composing the AFGLO in the direction of arrow 9. The blower 13 is for circulating the laser gas. By this blower 13, the flow velocity of laser gas is set around 100 m/sec in the DA 5 of the DT 1. The pressure of the LGCP is about 100 to 200 Torr. When a specific voltage is applied from the power supply unit 4, the DA 5 discharges. By this discharge and operation of the blower, the temperature of the laser gas climbs up. The heat exchangers 11 and 12 are for cooling the heated laser gas.
This is a structure of the conventional AFGLO, and its operation is explained.
The laser gas sent out from the blower 13 passes through the laser gas passage 10, and is led into the DT 1 through the lead-in part 14. In this state, when a specific voltage is applied to the electrodes 2, 3 from the power supply unit 4, the DA 5 discharges. The laser gas in the DA 5 obtains this discharge energy and is excited. The excited laser gas is resonated by the laser resonator composed of the RM 6 and OPM 7. As a result, a laser beam 8 is emitted from the OPM 7. This emitted laser beam 8 is utilized in laser processing and other applications.
Such conventional AFGLO had the following problems.
In the gas laser apparatus, the flow of laser gas in the DT 1 is preferred to be uniform from introduction of gas into the discharge tube until discharge, as far as possible, in the gas flow direction. If the gas flow is uniform, a stable discharge is obtained in the DA 5. When the discharge is stable, the laser output from an electric input injected for discharge becomes higher. That is, the efficiency of laser output is high in terms of the injected electric input. To make the laser gas uniform in the DT 1, the laser gas lead-in part may be formed coaxially with the DT 1. However, due to structural characteristics of the AFGLO, it is difficult to install the laser gas lead-in part coaxially with the DT 1. Accordingly, as shown in partial sectional views of the lead-in part 14 and DT 1 in FIG. 38 and FIG. 39 (FIG. 39 being a sectional view along line 39xe2x80x9439 in FIG. 38), the laser gas lead-in part 14 is composed of a lead-in pipe 142 disposed nearly at right angle to the DT 1, and a chamber 144 communicating with the laser gas passage 10 at the upstream side of the lead-in pipe 142. The laser gas flows from the chamber 144 into the DT 1 through the lead-in pipe 142. In this structure, the laser output characteristic (L102) is shown in FIG. 40. FIG. 40 shows the laser output with respect to the electric input to the discharge tube. In FIG. 40, the axis of abscissas denotes the discharge electric input, and the axis of ordinates represents the laser output. As shown in FIG. 40, as the discharge electric input into the DT 1 increases, the laser output saturates. In this structure, the discharge tended to be deviated in the outer circumference of the discharge tube. This deviation of discharge is visually recognized. Considering from this deviation of discharge, it is estimated that the gas flow is not uniform in the discharge tube. For example, the flow of laser gas from the lead-in pipe 14 into the DT 1 is estimated as shown in FIG. 41, that is, a gas flow disturbance (vortex) 18 is formed in the DT 1, especially near the gas lead-in pipe 142.
Further, as shown in partial sectional views of the lead-in part 14 and DT 1 in FIG. 42 and FIG. 43 (FIG. 43 being a sectional view along line 43xe2x80x9443 in FIG. 42), an orifice 15 is disposed between the DT 1 and the lead-in pipe 14. The orifice 15 is composed of a portion for impeding the flow of laser gas, and one hole 16 for passing laser gas. The hole 16 of the orifice 15 is deviated from the center. In this case, the laser output characteristic (L104) is as shown in FIG. 44. As clear from FIG. 44, as the discharge electric input into the DT 1 increases, the laser output saturates, but as compared with the structure shown in FIG. 38, the laser output is slightly improved. However, in this structure, too, same as in the structure in FIG. 38, the discharge tended to be deviated into the outer circumference of the discharge tube. Considering from this result, for example, the flow of laser gas from the lead-in pipe 142 into the DT 1 is estimated as shown in FIG. 45, that is, a gas flow disturbance (vortex) 18 is formed in the DT 1, especially near the gas lead-in pipe 142.
Further, for example, Japanese Laid-open Patent No. 7-142787 discloses a structure in which a chamber for temporarily storing gas is provided, and it is connected to the laser gas lead-in part. This structure is intended to eliminate deviation of gas flow in the discharge tube by canceling directivity of laser gas flowing into the laser gas lead-in part. Also by disposing the laser gas lead-in part in a ring form around the discharge tube, it is attempted to dispose the laser gas lead-in part coaxially with the discharge tube. As investigated by the present inventors, in a same structure as in Japanese Laid-open Patent No. 7-142787, it is found that the laser gas flow in the discharge tube tends to deviate the discharge either into the central part or into the outer circumference of the discharge tube. This deviation of discharge can be visually recognized. Considering from this deviation of discharge, it is estimated that the gas flow is not uniform in the discharge tube. Besides, the structure is complicated.
To solve the above problems, the invention comprises a discharge tube for passing laser gas inside and exciting laser gas, a laser gas lead-in pipe connected to the discharge tube for leading the laser gas into the discharge tube, and a laser gas relay pipe for supplying laser gas into the laser gas lead-in pipe, and having a portion for allowing the laser gas to flow parallel to the flowing direction of the laser gas in the discharge tube. The flowing direction of laser gas in the laser gas relay pipe is parallel to and in the same direction as the flowing direction of the laser gas in the discharge tube.
The invention further comprises a discharge tube for passing laser gas inside and exciting laser gas, a laser gas lead-in pipe connected to the discharge tube for leading the laser gas into the discharge tube, and an orifice disposed near the junction of the discharge tube and laser gas lead-in part, in which the orifice is formed of a portion for impeding the flow of laser gas and plural holes for passing laser gas, and at least one hole is deviated from the center.
Moreover, the invention comprises a discharge tube for passing laser gas inside and exciting laser gas, a laser gas lead-in pipe connected to the discharge tube for leading the laser gas into the discharge tube, a laser gas relay pipe for supplying laser gas into the laser gas lead-in part, and an orifice disposed near the junction of the laser gas lead-in pipe and discharge tube, in which the laser gas relay pipe has a portion of allowing the laser gas to flow parallel to the flowing direction of laser gas in the discharge tube, and the orifice is formed of a portion for impeding the flow of laser gas and plural holes for passing laser gas, and at least one hole is deviated from the center.